1. Field of the Invention
The invention relates to a process for preparing fluorinated acetophenones from fluorinated aryl compounds in the presence of N-hydroxyphthalimides.
2. Brief Description of the Prior Art
Fluorinated acetophenones, especially 3-trifluoromethylacetophenone, are valuable intermediates for the synthesis of active agrochemical or pharmaceutical ingredients (see also EP-A 460 575).
Acylated aromatics are prepared customarily by directly acylating aromatics in the presence of Lewis acids, but may also be prepared, for example, by oxidizing alpha-hydroxyalkylaromatics or isoalkylaromatics with N-hydroxyphthalimide (see also EP-A 796 835; Y. Ishii et al., Catalysis Surveys from Japan, 1999, 3, 27–35; Y. Ishii et al., Adv. Synth. Cat., 2001, 5, 393–427). A disadvantage of the processes is that they are restricted to electron-rich aromatics and the latter method typically proceeds with little selectivity. For fluorinated and other electron-deficient aromatics, the synthesis is generally effected via the steps of nitration, reduction of the nitroaromatic to the corresponding aniline and diazotization with aldoxime to the corresponding acetophenone. A disadvantage of this process is that it proceeds over several stages and thus requires a high degree of apparatus complexity, and also that the overall yield is only moderate.
There is therefore a need to provide an efficient process for preparing fluorinated acetophenones starting from readily available reactants.